High-speed scanners are commercially available which generate a high-density cloud of point measurements. Such scanners typically have a rotating element which scans a measurement beam about a first axis, mounted on a support which rotates about an orthogonal axis. Each point measurement typically includes a horizontal angle, a vertical angle, a range and a signal intensity. Scanners of this general type include the Trimble Cx Scanner and the Trimble Fx Scanner available from Trimble Navigation Limited of Sunnyvale, Calif., USA.
A single stationary scan involves operating the scanner at a selected location to obtain a set of of point measurements for that location. A project involves performing such a scan at each of multiple locations to obtain data representing a cloud of points for a three-dimensional environment of interest. A user may perform, for example, some fifty scans per day with such a scanner. A typical project can include 200 to 2000 or more scans. Each scan typically includes between 50-150 million point measurements. A single project of 200 scans each having 100 million point measurements, for example, would produce data representing some 20 giga-points. Projects of 7000 scans are already known, and even larger projects are expected in future.
The huge size of these data sets raises a number of issues. First, is how to store and transfer the data from the project site where the data is collected to an office environment where the data are needed. The currently preferred method is to store the data on a physical storage medium, such as a hard drive, and to ship this medium by post or courier. Streaming of such large data sets is generally impractical.
Second, is how to process the data. Special processing algorithms, such as are used to extract useful information from the raw point-measurement data, are slow due to the large quantity of data to be manipulated and the sequential structure of the acquired data set.
Third, is how to present the data so they can be visualized. Visualization is needed in the field for quality assurance so the scanner operator can assure the collected data set is good, as well as in the office where the data are used.
Fourth, is how to recover when a scan is interrupted before, completion, such as when battery power is lost during a scan, so that already-acquired data are not lost.
Improved methods and apparatus for managing such point cloud data are needed to address one or more of these and other issues.